The present invention relates to a fuel injection device for an internal combustion engine, such as those typically used in a motor vehicle, and more particularly to a device by which the fuel-air mixture is uniformly distributed into each of the combustion chambers in an engine.
FIG. 1 shows a conventional fuel injection device in which the fuel injection valve 3 is vertically installed above the throttle valve 2, which is rotatably mounted in the throttle bore 4 of the throttle body 5. The throttle valve 2 rotates when the operator of the vehicle moves or depresses the accelerator. The fuel injection nozzle of the fuel injection valve 3 is oriented so that the fuel is directed toward the downstream area of throttle valve 2, which in FIG. 1 corresponds to the left side of the throttle bore 4. The fuel supply injected by valve 3 enters in the approximate form of a hollow circular cone which is injected into the opening defined by the outer periphery of the throttle valve 2 and the throttle bore 4. The center line of the fuel injection valve 3 coincides with the center line of the throttle body 5 and the center line of the throttle bore 4. Fuel is supplied to the fuel injection valve 3 of the fuel supply passage 6. If there is any excessive accumulation of fuel in the injection valve, it is returned to the fuel tank through the fuel return passage 7. The cavity 8 houses an electric connector which controls the fuel injection valve 3. The fuel supply passage 6 and the cavity 8 are contained in the supporting bar 9, which projects from the throttle body 5 into the throttle bore 4 and supports the fuel injection valve 3. The fuel return passage 7 is located in a second supporting bar 10, which projects into the throttle bore 4 in the opposite direction from the first supporting bar 9 and assists in supporting the fuel injection valve 3.
The fuel injected by the fuel injection valve 3 passes the throttle valve by one of two methods: it either hits the upstream side of the valve (right end of throttle valve 3 in FIG. 1) and then flows across the valve to the downstream side (left end of throttle valve 2 in FIG. 1), and into the manifold (not shown in drawings) or it is injected directly into the manifold area without contacting the throttle valve 2. This results in the injected fuel gathering on one side of the throttle bore 4, causing a non-uniform distribution of fuel into each cylinder of a multi-cylinder engine. It is generally preferred for the injected fuel to create a fuel cone injection angle .theta. which ranges somewhere between 60.degree. to 90.degree..
This non-uniform distribution of fuel becomes more prevalent when the atmospheric temperature is low or there is a substantial difference in the shape of each intake manifold. This non-uniform fuel distribution results in lower engine output, rough engine idling and even more important, the presence of a transitional response (hesitation) of engine power dependent upon the opening angle of throttle valve 2.